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Title: Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle

Abstract

We study the density modulation that appears in a Bose-Einstein condensate flowing with supersonic velocity against an obstacle. The experimental density profiles observed at JILA are reproduced by a numerical integration of the Gross-Pitaevskii equation and then interpreted in terms of Cerenkov emission of Bogoliubov excitations by the defect. The phonon and the single-particle regions of the Bogoliubov spectrum are, respectively, responsible for a conical wave front and a fan-shaped series of precursors.

Authors:
 [1]; ;  [2];  [2];  [3]
  1. CNR-BEC-INFM, Trento, I-38050 Povo (Italy)
  2. Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)
  3. (Italy)
Publication Date:
OSTI Identifier:
20861534
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97; Journal Issue: 26; Other Information: DOI: 10.1103/PhysRevLett.97.260403; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOSE-EINSTEIN CONDENSATION; CHERENKOV RADIATION; EQUATIONS; EXCITATION; MODULATION; PHONONS

Citation Formats

Carusotto, I., Hu, S. X., Collins, L. A., Smerzi, A., and CNR-BEC-INFM, Trento, I-38050 Povo. Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.97.260403.
Carusotto, I., Hu, S. X., Collins, L. A., Smerzi, A., & CNR-BEC-INFM, Trento, I-38050 Povo. Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle. United States. doi:10.1103/PHYSREVLETT.97.260403.
Carusotto, I., Hu, S. X., Collins, L. A., Smerzi, A., and CNR-BEC-INFM, Trento, I-38050 Povo. Sun . "Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle". United States. doi:10.1103/PHYSREVLETT.97.260403.
@article{osti_20861534,
title = {Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle},
author = {Carusotto, I. and Hu, S. X. and Collins, L. A. and Smerzi, A. and CNR-BEC-INFM, Trento, I-38050 Povo},
abstractNote = {We study the density modulation that appears in a Bose-Einstein condensate flowing with supersonic velocity against an obstacle. The experimental density profiles observed at JILA are reproduced by a numerical integration of the Gross-Pitaevskii equation and then interpreted in terms of Cerenkov emission of Bogoliubov excitations by the defect. The phonon and the single-particle regions of the Bogoliubov spectrum are, respectively, responsible for a conical wave front and a fan-shaped series of precursors.},
doi = {10.1103/PHYSREVLETT.97.260403},
journal = {Physical Review Letters},
number = 26,
volume = 97,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 2006},
month = {Sun Dec 31 00:00:00 EST 2006}
}
  • Using stationary solutions of the linearized two-dimensional Gross-Pitaevskii equation, we describe the wave pattern occurring in the supersonic flow of a Bose-Einstein condensate past an obstacle. It is shown that these waves are generated outside the Mach cone. The developed analytical theory is confirmed by numerical simulations of the flow past body problem in the frame of the full nonstationary Gross-Pitaevskii equation. Relation of the developed theory with recent experiments is discuss0008.
  • We use the one-dimensional (1D) Gross-Pitaevskii equation to investigate the dynamical evolution of a dilute repulsive Bose-Einstein condensate (BEC) confined in an elongated static nonharmonic trap and stirred by an oscillating Gaussian obstacle moving at uniform speed in alternate direction. Direct numerical solutions of this equation show that above a critical obstacle velocity, the motion of the obstacle creates gray solitons and phonons. At first, when the velocity of the obstacle increases, the dissipation also increases. But the dissipation reaches a maximal value and then decreases dramatically and vanishes at high obstacle velocities. Our results at low obstacle velocities aremore » similar to those previously obtained experimentally and by simulations in the case of vortice and phonon production in 3D and 2D trapped repulsive BEC's. But at high obstacle velocities, we show that the quasi-1D trapped repulsive BEC behaves as a quasisuperfluid medium with disappearance of gray soliton and phonon excitations. This extends previous results and provides the main dependence of the phenomenon on the obstacle characteristics.« less
  • A theory of linear wave patterns developing in Bose-Einstein condensate flow past an obstacle is developed. The results obtained characterize the wave crestline geometry and the far-field dependence of the wave amplitude on coordinates. The theoretical predictions agree with the results of previous numerical simulations and provide a qualitative explanation of experiments on the flow of a Bose-Einstein condensate released from a trap past an obstacle.
  • The stability of dark solitons generated by supersonic flow of a Bose-Einstein condensate past an obstacle is investigated. It is shown that in the reference frame attached to the obstacle a transition occurs at some critical value of the flow velocity from absolute instability of dark solitons to their convective instability. This leads to the decay of disturbances of solitons at a fixed distance from the obstacle and the formation of effectively stable dark solitons. This phenomenon explains the surprising stability of the flow picture that has been observed in numerical simulations.
  • We report the observation of highly energetic self-interfering matter-wave (SIMW) patterns generated by a moving obstacle in a two-dimensional Bose-Einstein condensate (BEC) inside a power trap cut off by hard-wall box potential boundaries. The obstacle initially excites circular dispersive waves radiating away from the center of the trap which are reflected from hard-wall box boundaries at the edges of the trap. The resulting interference between outgoing waves from the center of the trap and reflected waves from the box boundaries institutes, to the best of our knowledge, unprecedented SIMW patterns. For this purpose we simulated the time-dependent Gross-Pitaevskii equation usingmore » the split-step Crank-Nicolson method and the obstacle was modelled by a moving impenetrable Gaussian potential barrier. Various trapping geometries are considered in which the dynamics of the spatial and momentum density, as well as the energy, are considered. The momentum dynamics reveal an oscillatory behavior for the condensate fraction, indicative of excitations out of and de-excitations back into the condensate state. An oscillatory pattern for the energy dynamics reveals the presence of solitons in the system. Some vortex features are also obtained.« less